The increase in traffic density and more and more construction taking up free areas are reducing the traffic space continuously, in particular in densely populated areas. Available parking spaces are becoming scarcer, and the search for suitable parking spaces puts a stress on the driver in addition to the constantly increasing traffic. In particular in backing into a parking space, correctly estimating the exact size and position of the parking space is often associated with considerable difficulties. Some drivers are often unsure whether their vehicle fits into a parking space that they have found, which is formed between stationary vehicles or other obstacles.
Conventionally, different devices and systems are used for unburdening the driver of a vehicle when parking. For example, parking pilots for distance detection of the objects delimiting the parking space in the front and back area of the vehicle (PDC=Park Distance Control), parking space measuring systems (PSM), and semi-autonomous or fully autonomous parking assistants have been proposed.
Multiple methods and systems for assisting the driver in ascertaining suitable parking spaces with the aid of parking space measurement are described, for example, in German Patent Application Nos. DE 102 58 310 A1, DE 103 20 723 A1, and DE 102 57 722 A1. In a parking sequence, the first important task for the driver is to estimate whether the length and depth, i.e., width, of a potential parking space is sufficiently large for parking the vehicle and whether it is thus possible to safely park the vehicle in this parking space. To facilitate this estimate, a parking space measuring system (PSM) is used, which measures the parking space dimensions between two parked vehicles. For this purpose, when driving by a potential parking space, contactless distance sensors which may preferably be formed by ultrasonic sensors, but also by infrared or radar sensors, for example, first detect a first stationary obstacle; then detect, over a certain stretch, an at least essentially obstacle-free potential parking space, and then a second stationary obstacle. The length and/or depth of the space thus measured and/or information derived therefrom regarding whether his vehicle fits into this space between the obstacles may then be output to the driver.
German Patent Application No. DE 197 03 517 A1 describes a method and a device for assisting the driver in parking in a parking space after it has been measured. For this purpose, the required control interventions may be either displayed to the driver or also performed automatically as a parking assistant (PSC=Park Steering Control). The start of the parking sequence does not start until the driver has input an appropriate confirmation signal. It is further known to start parking immediately following the measurement or to start parking when a conclusion regarding a parking intent of the driver may be drawn on the basis of the driving conditions of the vehicle, which may be derived, for example, from the driver having stopped the vehicle.
Furthermore, German Patent No. DE 38 13 083 A1 describes an automatic parking device for motor vehicles in which potential parking spaces are measured when driving by and a signal is generated if a parking space is sufficiently large for parking. Also in this case, signals may be generated for performing the parking, these signals either being displayed in a display device to show the driver instructions for the required parking motions or controlling the drive mechanisms of the vehicle with the aid of control devices to achieve the necessary driving action. Regarding the start of the parking sequence, it is provided that the data for controlling the vehicle may contain a stop point at which the forward motion of the vehicle is stopped and the reverse motion of the parking sequence begins.
In conventional methods and systems of assistance in searching for a suitable parking space, the driver, however, still has to perform certain actions himself, which are associated with some difficulties. In particular, the driver must be active to stop the vehicle to enable the start of an assisted parking sequence. This creates difficulties, since on the one hand he must respond quickly in order not to be forced to back up too far. On the other hand, he must brake using sufficient care in order not to cause being back-ended by the vehicle following behind.
In addition, the driver himself must be careful not to exceed a maximum speed predefined by the system, since a safe and error-free detection and measurement of a parking space is not ensured above this speed. This is also due, among other things, to the physical limitations of the normally used ultrasonic sensors which provide reliable information about suitable parking spaces without problems only at a maximum speed of approximately 20 km/h or at corresponding maximum speeds for other sensor types. The driver must also constantly pay attention not to exceed the maximum speed supported by the system, which may furthermore depend on environmental conditions such as, for example, weather, wetness, ambient noise, and/or surrounding construction, if he wishes to avoid passing by suitable parking spaces without using them or parking spaces being erroneously signaled as suitable. This is very difficult over longer distances, particularly at low speeds.
Stronger support for the driver would therefore be desirable in looking for suitable parking spaces.